1. Field of the Invention
The present invention relates to an image forming apparatus or the like that performs a processing of supplying a colorant for each color, and more particularly to an image forming apparatus or the like that can reliably and rapidly perform a correction processing with respect to the so-called registration shift occurring due to the processing of supplying the colorants.
2. Description of the Related Art
In an image forming apparatus such as a laser printer, a processing of supplying colorants of different colors and causing the adhesion of the colorants to paper, an intermediate medium, or a photosensitive body is performed independently for each color. A problem that is sometimes encountered is that the formed images of different colors are shifted with respect to each other due to insufficient mechanical accuracy of the apparatus. When such registration shift (also called “color shift”) occurs, it adversely affects the output quality, for example, producing white portions (drop-out white) that have not been initially present on the boundaries of characters and background. For this reason, a processing of correcting the image data of the output image in advance is typically performed to prevent the defects caused by such registration shift.
Japanese Patent No. 3852234 suggests an apparatus in the related technical field that prevents effectively the so-called edge light coloring and performs rapid processing.
Japanese Patent Application Laid-open No. 2002-165104 describes an apparatus that performs a trapping processing such that an object seems to be of the same order as an actual one even when the plate shift occurs.
However, in the apparatus described in Japanese Patent No. 3852234, because a region where image data are corrected is determined in object units of the image, when an object that has to be corrected originally, such as text or graphics, is included by an object such as an image that does not corrected at an application stage from which image data are supplied, the correction is not performed with respect to these objects and reliable correction processing is not performed. Further, image data received by an image forming apparatus such as a printer are represented in PDL of various formats and the classification of objects is established for each format. Therefore, in the aforementioned processing in object units, a respective processing procedure has to be prepared for each format and the processing becomes complex and inefficient.
On the other hand, in a most general usage mode of image forming apparatuses, such as business use, drop-out white caused by the registration shift that occurs between the black text or graphic and a color background becomes a serious problem, and no method resolving this problem has been suggested.
Therefore, an efficient method for resolving this problem encountered in business use is needed in processing in pixel units that is considered to be a time-consuming processing.